SSC CGL GENERAL INTELLIGENCE: OSI LAYERS- DEVICES & PROTOCOLS (LECTURE 3)
- Developed by International Standards Organization (ISO)
- Divides network communication into seven layers.
- Layers 1-4 are considered the lower layers, and mostly concern themselves with moving data around.
- Layers 5-7, the upper layers, contain application-level data.
- Control is passed from one layer to the next, starting at the application layer in one station, and proceeding to the bottom layer, over the channel to the next station and back up the hierarchy.
7 LAYERS OF OSI MODEL
- Physical (Layer 1) |———- Logical Link Layer
- Data Link (Layer 2)—Sublayers——-
- Network (Layer 3) |———- Media Access Control
- Transport (Layer 4)—- TCP (Connection Oriented) & UDP (Connection Less)
- Session (Layer 5)
- Presentation (Layer 6)
- Application (Layer 7)
Now, Let us discuss each layer.
PHYSICAL LAYER: Provides the hardware means of sending and receiving data on a carrier, including defining cables, cards and physical aspects.
DATA LINK LAYER: Furnishes transmission protocol knowledge and management and handles errors in the physical layer, flow control, and frame synchronization.
NETWORK LAYER: Provides switching and routing technologies, creating logical paths, known as virtual circuits, for transmitting data from node to node. Routing, forwarding, addressing, internetworking, error handling, congestion control, and packet sequencing are functions of this layer.
TRANSPORT LAYER: Provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control. It ensures complete data transfer.
SESSION LAYER: Establishes, manages and terminates connections between applications. The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end. It deals with session and connection coordination.
PRESENTATION LAYER: Provides independence from differences in data representation (e.g., encryption) by translating from application to network format, and vice versa.
APPLICATION LAYER: Supports application and end-user processes. Provides application services for file transfers, e-mail, and other network software services. Telnet and FTP are applications that exist entirely at the application level. Tiered application architectures are part of this layer.
NETWORK SECURITY AND HACKING
IEEE 802 STANDARD PROTOCOL-
802.1 – LAN/ MAN Bridging
802.2 – Logical Link Control
802.3 – Ethernet
802.4 – Token Bus
802.5 – Token Ring
802.6 – MAN
802.7 – Broadband LAN
802.8 – Fiber Optics
802.9 – Integrated LAN Services
802.10- Interoperable LAN Security
802.11 – WiFi
802.12- Demand Priority
802.13- Not used
802.14- Cable Modems
802.15 – Wireless Personal Area Networks
802.15.1 – Bluetooth
802.16 – Wireless MAN
802.22 – Wireless Regional Area Network
COMPUTER NETWORK & TYPES (LECTURE 1)
DEVICES & PROTOCOLS IN EACH LAYER
Physical (Layer 1): Ethernet, FDDI, USB, REPEATER, HUB, B8ZS, V.35, V.24, RJ45, RS232, and ATM
Data Link (Layer 2): SWITCH, BRIDGE, NIC, LAN CARD, PPP, FDDI, ATM, IEEE 802.5/ 802.2, IEEE 802.3/802.2, HDLC, Frame Relay.
Network (Layer 3): AppleTalk DDP, IP, IPX.
Transport (Layer 4): SPX, TCP, UDP.
Session (Layer 5): NFS, NetBios names, RPC, SQL
Presentation (Layer 6): SYNTAX, Encryption, File Formats, ASCII, EBCDIC, TIFF, GIF, PICT, JPEG, MPEG, MIDI.
Application (Layer 7): SOFTWARE, EMAIL, SERVICE, DNS, DHCP, WWW browsers, NFS, SMTP, Telnet, HTTP, FTP
NOTE: Gateway is the only device which works on all the 7 layers.
Students, please learn them before exams. We will be covering another important topic in next article. Stay Updated with Kailasha Foundation. You can also tell us if you want us to cover any specific topics or subjects.
SOURCE: Based on Self-Knowledge
IMAGE SOURCE: Google